NR: Design and Evaluation of Retrieval Functions in Peer-to-Peer File Sharing Systems

对等（P2P）文件共享系统允许在分布式端系统或对等体之间共享内容。文件存储在对等体上，并直接在它们之间传输。在过去的几年里，这种系统的普及程度大大提高。除了它们最近的流行之外，点对点系统代表了一种重要的新内容交付范式，从长远来看，它有可能重新塑造互联网的架构和性能。一个典型的P2P用户会话包括一个搜索阶段，其中可以进行多个搜索，然后是一个检索阶段，其中可以请求多个文件。许多研究和开发已经进入了不同的文件搜索系统的设计，目的是提高性能和鲁棒性。在拟议的工作中，研究人员专注于文件检索阶段，这是迄今为止较少受到研究界的关注。我们的动机有三个主要的观察：（一）P2P系统用户的体验是搜索以及检索功能的性能的总和;（二）在检索阶段使用的网络资源可以远远超过在搜索阶段消耗的资源。因此，新的范例和改进的检索阶段的设计可以有深远的影响，在一般的互联网上的性能;（iii）一个P2P系统提供了一个显着不同的上下文内容检索比更传统的客户端-服务器模型，他们有更大规模的内容复制，同行可能拥有严重的资源限制，和同行是相当动态的。我们的研究包括三个方面：1。改进检索阶段性能的对等体选择策略。研究者研究了这个问题的两个方面，这是P2P环境所特有的，并且很少受到关注：（i）由于P2P系统中固有的大规模复制，搜索阶段只能发现可用副本的子集，以及（ii）服务对等点的约束性质，可能需要阻止请求，直到服务容量可用。同时涉及多个服务对等体的内容检索策略。P2P系统中可能存在的大规模复制导致了并行地从多个对等体执行文件检索的有趣的可能性，以提高性能并克服对等体动态性和不稳定性。这项工作考虑了大规模部署并行下载的性能以及网络用户之间的公平性的影响。此外，我们的工作在这种背景下重新审视选择问题。P2P系统运行的整体方法。目标是改善整体P2P用户搜索和检索体验。我们引入了一个新的维度，搜索的质量，应该判断搜索阶段的结果的性能和它的效果在检索阶段的性能。研究人员研究现有的搜索技术与这个新的视角，也考虑两个搜索范式的启发，以前的工作分布式匹配算法和广播流scheduling.The研究成果将包括理论以及上述领域的实际研究。研究人员将使用各种技术来评估我们的想法（包括数学和理论分析、模拟、仿真和实验）。这项工作将是第一个深入研究P2P系统中的检索阶段。由于网络资源的使用主要是由检索阶段的要求，这项工作也将提供的P2P系统对互联网资源的影响的理解的基础，并进一步指导供应努力，以满足P2P系统的需求。我们还致力于将促进拟议工作的更广泛影响的活动，包括：（一）根据我们的研究为研究生和本科生课程开发模块，（二）继续强调在我们的研究工作中纳入代表性不足的群体，以及（三）外联活动，以亚特兰大为基础的历史上黑人学院和大学。

Peer-to-peer (P2P) file sharing systems allow content to be shared between distributed end-systems or peers. Files are stored at the peers and transferred directly between them. The last few years have seen the popularity of such systems grow tremendously. Beyond their recent popularity, peer-to-peer systems represent a significant new content delivery paradigm that has the potential to re-shape the architecture and performance of the Internet in the long term. A typical P2P user session consists of a search phase where multiple searches may be conducted followed by a retrieval phase in which multiple files may be requested. Much research and development has gone into the design of differing systems for file search, with the aim of improving performance and robustness. In the proposed work, the researchers focus on the file retrieval phase, which has so far received less attention from the research community. We are motivated by three main observations: (i) A P2P system user's experience is the sum total of the performance of both the search as well as the retrieval functions; (ii) The network resources used during the retrieval phase can outweigh by far the resources consumed during the search phase. As such, new paradigms and improvements in the design of the retrieval phase can have far reaching implications on the performance of the Internet in general; (iii) A P2P system provides a significantly different context for content retrieval than the more traditional client-server model; they have larger scale content replication, the peers may possess severe resource constraints, and the peers are quite dynamic. Our proposed research encompasses three areas:1. Peer selection strategies for improved performance of the retrieval phase. The resesearchers examine two aspects of this problem that are unique to the P2P environment and that have received little attention: (i) the fact that, due to the large-scale replication inherent in P2P systems, the search phase can only discover a subset of available replicas, and (ii) the constrained nature of serving peers which may require requests to block until serving capacity is available.2. Content retrieval strategies involving multiple serving peers simultaneously. The large scale replication that may be present in P2P systems leads to the interesting possibility of performing file retrieval from multiple peers in parallel, both to improve performance and overcome peer dynamics and instability. This work considers the effect of wide-scale deployment of parallel downloading on performance as well as fairness among network users. In addition, our work revisits the selection problem in this context.3. A holistic approach to the operation of P2P systems. The objective is to improve overall P2P user search and retrieval experience. We introduce a new dimension, the quality of a search, by which one should judge the performance of the outcome of a search phase and its effect on the performance during the retrieval phase. The researchers study existing search techniques with this new perspective and also consider two search paradigms inspired by prior work on distributed match-making algorithms and broadcast-stream scheduling.The research output will consist of theoretical as well as practical studies of the areas described above. THe researchers will use a variety of techniques to evaluate our ideas (including mathematical and theoretical analysis, simulation, emulation, and experimentation). This work will be among the first to study the retrieval phase in P2P systems in depth. Because network resource usage is primarily influenced by the retrieval phase requirements, this work will also provide the basis of an understanding of the effect of P2P systems on Internet resources and further guide provisioning efforts to meet the demands of P2P systems. We are also committed to activities that will promote the broader impact of the proposed work including: (i) development of modules based on our research for graduate and undergraduate classes, (ii) continued emphasis on inclusion of under-represented groups within our research efforts and (iii) outreach activities to Atlanta-based historically black colleges and universities.